Method of forming surface acoustic wave tag-based gas sensors

A method for fabricating a sensor system, comprising:

• providing a surface acoustic wave (SAW) tag on a substrate, the SAW tag including a detector bank of reflectors at one end of the substrate to generate a detector SAW in response to an interrogation signal, a reference bank of reflectors at an opposite end of the substrate to generate a reference SAW in response to the interrogation signal, and a transducer on the substrate between the detector and reference banks of reflectors for receiving the interrogation signal and transmitting the detector SAW and the reference SAW from the detector and the reference banks of reflectors in response, and
• forming a hydrogen gas sensor on the substrate in a propagation delay path (delay path) between the detector bank of reflectors and the transducer to modulate propagation parameters of the detector SAW in response to sensing hydrogen gas, wherein the forming comprises:
• depositing a tin-dioxide (SnO2) film onto the delay path;
• depositing a palladium (Pd) film onto the SnO2 film, and
• annealing the hydrogen gas sensor.